Sometimes referred to as a Faraday cage, the Faraday shield is a metallic device that is designed to block and focus electric fields. Often constructed as a sheet of metal, this device is used in several different types of applications, ranging from telecommunications to medical equipment.

The concept of the Faraday shield was first developed by Michael Faraday, a physicist with a special interest in the control of electricity fields. Beginning in 1836, Faraday built and explained the function of Faraday shields. The earliest of these Faraday cages or shields were in the form of a metal enclosure, often using a metal mesh to create an enclosed space for the transmission of current or waves. Faraday saw the shield as a way of preventing various electromagnetic waves from bisecting and interfering with one another. The Faraday shield would make it possible to operate multiple pieces of machinery within close proximity to one another, with no electrical interference occurring.

In modern construction, this shield is essentially a set of parallel wires that are attached to a common conductor at one end. The conductor is grounded and helps to form an enclosure that helps to focus the electrostatic field. At the same time, the device helps to prevent interference from other electrical waves from interfering with the flow of power within the enclosure.

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Over time, the applications for the Faraday shield have developed for a number of industries. The concept of the shield revolutionized the idea of wiring buildings for electrical service, ensuring the safe operation of multiple appliances at the same time. Communications is one example of an industry that benefited early on from the Faraday shield. Shields were installed in transmission switches and towers to help prevent radio waves from scattering and interfering with other equipment. The Faraday shield continued to expand its presence with the advent of television, and still plays an essential role in such modern technology as wireless communications and computer networking.

The medical profession also employs this device. One of the more common applications is with MRI equipment. The shields are used in many MRI rooms prevent stray radio waves from entering the room and impacting the imaging process. This allows the equipment to provide a clear image that can result in a more accurate diagnosis and treatment.

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